There are many devices which facilitate the inhalation of powdered medicaments by the use of propellants, such as compressed or liquified gases, to dispense and disperse the medicament. These devices may be complex to construct and have the disadvantage that in order for the optimum effect to be obtained it is essential that inhalation and dispensing be synchronous.
There are also a number of known breath-actuated inhalation devices for administering powdered medicaments to the lungs. The powdered medicament is typically supplied in commercially available capsules which comprise first and second capsule portions, each including a tubular part having an open end and an end wall opposite its open end, with the open end and tubular part of one portion being received through the open end of the other of the tubular parts in mechanical or frictional engagement to retain the powdered medicament therein. In the simpler breath-actuated devices the capsule is opened prior to insertion into the device and one capsule portion containing the medicament or the medicament itself is positioned in the device such that during inhalation through the mouthpiece the medicament becomes entrained in the air stream and passes to the patient. Examples of such devices are disclosed in British Patent Specification Nos. 1,520,064; 1,504,441; 1,118,341; 1,520,063 and 1,520,062. These devices suffer from the disadvantage that medicament may be spilled when the capsule is opened prior to insertion in the device.
British Patent Specifications Nos. 1,521,000; 1,520,062; 1,472,650 and 1,502,150 disclose more complex devices in which the complete capsule is inserted into the device, thus ensuring no spillage of medicament prior to inhalation, and access to the medicament is gained by piercing the capsule or cutting it in half inside the dispensing device. On inhalation the air flows into or through the capsule and the powder within is entrained in the air stream and carried towards the mouth.
The devices disclosed in British Patent Specifications Nos. 1,485,163; 1,331,216; 1,457,352; 1,396,258; 1,182,779; 1,404,338; 1,459,426 and 1,118,341 and U.S. Pat. Nos. 4,117,844 and 4,116,195 are designed to agitate the capsule containing the medicament in order to help release and disperse the powder from the capsule. The capsule may be agitated by various means, including creating a turbulent air flow, or by rotating and/or vibrating the capsule through the use of vanes or propellers. These devices are complex and are often difficult to operate.
U.S. Pat. No. 4,210,140 discloses a device in which access to the powdered medicament is gained by pulling the capsule portions apart so that the medicament is emptied to a suitable position for entrainment in the air flow caused by inhalation.
Our copending PCT Publication No. 81/01243 discloses breath-actuated devices for the oral inhalation of powdered medicaments. Those devices each comprise a chamber having at least one inlet port for the entry of air and in direct communication with a mouthpiece; means within the chamber for holding a capsule containing a medicament substantially vertically; and means for separating the capsule portions within the chamber to expose the open end of the lowermost capsule portion and afford access to the powdered medicament within in a position such that when the device is operated by suction at the mouthpiece, air flows essentially transversely across the open end of the lowermost capsule portion, causing the particles of powdered medicament therein to become entrained in the air.
The devices described in that application are easy and simple to use, reduce the possibility of the user spilling the medicament and ensure that any medicament that is spilled will still be inhaled, and are very efficient when compared to breath-actuated devices of the prior art. Positioning the means for separating the capsule portions in the chamber, however, presents possibilities for air leaks into the chamber, and restricts the design possibilities to provide a desired air flow pattern through the chamber.